Kinetic Determination of Iodide Traces Based on the Manganese(III) Metaphosphate–Arsenic(III) Reaction in the Presence of Orthophosphoric Acid

The kinetics of the iodide-catalyzed Mn(III) metaphosphate–As(III) reaction was studied in the presence of orthophosphoric acid. The reaction rate was followed spectrophotometrically at 516nm. It was established that orthophosphoric acid increased the reaction rate and that the extent of the non-catalytic reaction was extremely small. A kinetic equation was postulated and the apparent rate constant calculated. The dependence of the reaction rate on temperature was investigated and the energy of activation and other kinetic parameters determined. Iodide was determined under the optimal experimental conditions in the range 0.6–2.5ng·mL^–1 with a relative standard deviation of up to 6.7% and a detection limit of 0.12ngmL^–1. The effect of foreign ions on the accuracy of the determinations was also investigated.     

Preparative purification of tetrabromotetrachlorofluorescein and phloxine B by centrifugal counter-current chromatography.

A centrifugal counter-current chromatographic method for preparative purification of commercial tetrabromotetrachlorofluorescein and Phloxine B (D&C Red Nos. 27 and 28, respectively) was developed. Ethyl acetate-n-butanol-0.01 M ammonium acetate (1:1:2) was used as the two-phase solvent system. Each purification trial involved 50 mg of sample and yielded 22 mg (+/- 2 mg) of pure dye. The purity of the product was measured by high-performance liquid and thin-layer chromatography and was found to be 99.9%. The partition coefficients of these compounds were found to be highly concentration-dependent in the two-phase solvent system used. If this problem can be circumvented, then the counter-current chromatographic method can be extended for use with gram quantities of dye.     

Zum Problem der Vervielfachung

Zusammenfassung Eine Methode zur jodometrischen Bestimmung von Kupfer, Nickel und Kobalt wurde beschrieben, bei der die Metalle zunächst elektrolytisch abgeschieden werden. Das Metall wird dann mit Silbernitratlösung umgesetzt, wobei eine äquivalente Menge Silber abgeschieden wird. Diese wird gelöst, als Silberjodid gefällt und nach Vervielfachung mit Thiosulfat titriert.

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Summary A method is described for the iodometric determination of copper, nickel and cobalt in which the metals are previously deposited electrolytically. The metal is then allowed to react with silver nitrate solution, with the result that an equivalent quantity of silver is deposited. The latter is dissolved, precipitated as silver iodide, and then after multiplication titrated with sodium thiosulfate.

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Herrn Prof. Dr.Hans Lieb zum 80. Geburtstag freundlichst gewidmet.     

A voltammetric identification of complex species inDMF solutions of Iron(III) complexes with salicylaldehydeS-methylthiosemicarbazone

The complex species existing under voltammetric conditions (0.1 mol dm^–3 LiCl) inDMF solutions of several iron(III) complexes with salicylaldehydeS-methylthiosemicarbazone (H₂ L) have been identified by adding [FeCl₄]^– and H⁺ and recording voltammograms at a glassy carbon electrode, both in stationary and rotating mode. By the action of Cl^–, a ligand release occurs, and the bis(ligand) cation [Fe(HL)₂]⁺ is transformed into [Fe(HL)Cl₃]^–. The same species is obtained in the reaction of [FeL ₂]^– with [FeCl₄]^–. Besides, the possibility has been demonstrated to obtain some complexes (and finally [FeCl₄]^–) starting from a more basic type, by a careful addition of H⁺ generatedin situ from a Pd/H electrode. A practical application of the latter procedure could be the determination of the iron(III) content in such and similar compounds.

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Die voltammetrische Identifizierung der Komplex-Spezies in DMF Lösungen von Eisen(III) Komplexen mit Salicylaldehyd-S-methylthiosemicarbazon

Zusammenfassung Die Spezies, die unter voltammetrischen Bedingungen (0.1 mol dm^–3 LiCl) inDMF Lösungen einiger Eisen(III)-Komplexe mit Salizylaldehyd-S-methylthiosemicarbazon (H₂ L) vorhanden sind, wurden durch Zusatz von [FeCl₄]^– und H⁺ und Aufnahme von Voltammogrammen an der stationären und rotierenden Glaskohlenstoffelektrode identifiziert. Unter der Wirkung von Cl^–-Ionen kommt es zu einem Ligandenaustausch, wobei das bis(Ligand)-Kation [Fe(HL)₂]⁺ in [Fe(HL)Cl₃]^– übergeht. Die gleiche Substanz erhält man bei der Reaktion von [FeL ₂]^– mit [FeCl₄]^–. Ferner wird die Möglichkeit der Gewinnung einiger Komplexe (schließlich von [FeCl₄]^–) ausgehend von der basischen Form durch stufenweise Zugabe von H⁺-Ionen, diein situ mit Hilfe einer Pd/H-Elektrode gebildet werden, beschrieben. Eine praktische Anwendung des letztgenannten Prozesses wäre die Bestimmung des Gehalts von Fe(III) in Lösungen der genannten und ähnlichen Komplexverbindungen.

     

Ein Beitrag zum Problem der Vervielfachung in der Mikroanalyse

Zusammenfassung Von einem VorschlagF. Emichs (1933) ausgehend, wurden Methoden zur Vervielfachung von Metallionen ausgearbeitet. Diese beruhen darauf, daß durch aufeinanderfolgende, stöchiometrisch verlaufende Umsetzungen die Masse der Bestimmungsform vergrößert wird. Alle diese Reaktionen können in einfacher Weise direkt auf Filterpapier ausgeführt werden. Die Methoden wurden zur halb quantitativen Analyse von Thallium, Chromat, Kupfer, Eisen und Zink mit Hilfe der Ringofentechnik herangezogen. Einige Analysenbeispiele zeigen die Brauchbarkeit des Verfahrens. Die Möglichkeiten dieser Vervielfachungsmethoden werden allgemein diskutiert.

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Summary On the basis of a suggestion byF. Emich (1933) methods were worked out for the multiplication of metal ions. They rest on the fact that the mass of the determination form is increased through successive stoichiometric reactions. All of these reactions can be conducted in simple manner directly on filter paper. The methods have been applied for the semi-quantitative determination of thallium, chromate, copper, iron, and zinc with the aid of the ring furnace technique. Several analysis examples demonstrate the feasibility of the method. The possibilities of these multiplication methods are discussed in general.

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Résumé A partir d'une suggestion deF. Emich (1933), on a mis au point des méthodes de multiplication des ions métalliques. Celles-ci reposent sur le fait que la masse de la forme du dosage se trouve augmentée par des réactions successives qui se produisent stoechiométriquement. Toutes ces réactions peuvent s'effectuer d'une manière simple directement sur papier filtre. On a employé ces méthodes pour l'analyse semi-quantitative du thallium, des chromates, du cuivre, du fer et du zinc par la technique du four annulaire. Un certain nombre d'exemples d'analyses montrent l'efficacité du procédé. On discute d'une manière générale les possibilités de ces méthodes de multiplication.

     

Stereospecific alcohol elimination from dialkyl mesaconates under electron impact: Another example of a hidden hydrogen transfer

Under electron impact dimethyl and diethyl mesaconates give rise to abundant [M ? MeOH]⁺ and [M ? EtOH]⁺ ions, respectively. The geometrically isomeric citraconates yield [M ? MeO]⁺ and [M ? EtO]⁺ ions. Mixed methyl ethyl mesaconates eliminate both methanol and ethanol. These findings, together with the results of a deuterium labelling study, indicate that the elimination of alcohol from the molecular ions of the mesaconates is partially preceded by a hidden hydrogen transfer step.     

Cyclopentadienylation of PVC: Characterization and thermal and thermooxidative degradation studies

PVC has been cyclopentadienylated by two conventional basic, LiCp and NaCp, and a new acidic, Me₂CpAl, cyclopentadienylating agent. PVCs treated with basic cyclopentadienylating agents undergo severe random dehydrochlorination and exhibit a significant decrease in thermal and thermooxidative stability. In contrast, according to ozonization and degradation experiments, Me₂CpAl does not cause dehydrochlorination during cyclopentadienylation. The thermal stability of PVC treated with relatively high concentrations of Me₂CpAl and Me₃Al at 25°C markedly increases due to substitution of labile chlorines in PVC with methyl groups. Initial thermal dehydrochlorination behavior of virgin PVC and samples treated with Me₂CpAl at ?30°C are similar. In contrast, thermooxidative stability decreases on Me₂CpAl treatment at ?30°C; this is attributed to ease of oxidation of pendant cyclopentadienyl groups; that is, the formation of peroxy radicals that may initiate dehydrochlorination by attacking unchanged repeat units in PVC. Acceleration of thermal dehydrochlorination disappears and the length of polyene sequences is reduced on Me₂CpAl and Me₃Al treatment. These observations are attributed to differences in rates of protonation-deprotonation; that is, rates of reinitation of zipping of treated and untreated PVCs during thermal degration. The effect of traces of aluminum residues on degradation of modified PVCs, however, cannot be neglected.     

Participation of halogen atoms in hydrogen transfer between remote positions in gas-phase ionized isomeric haloresorcinols

Mono, di- and trihaloresorcinols substituted by a halogen atom at position 2 exhibit a highly specific elimination of H₂O on electron impact ionization and under conditions of collisionally induced dissociation (CID). The high isomer specificity suggests the intermediacy of a hydrogen transfer from one of the hydroxy groups to the adjacent halogen atom. A subsequent hydrogen migration to the other hydroxy group readily explains the facile elimination of H₂O from the M^+· ions of these particular isomers. An analogous three-step hydrogen transfer has not been observed in 2,3-dihalo-l,4-hydroquinones. 4-Bromo- and 4-icdoresorcinol undergo elimination of the halogen atom followed by a very fast loss of CO under CID conditions, affording [M ? Hal]⁺ ions of low abundance and highly abundant[M ? Hal ? CO]⁺ ions. The elimination of CO is suppressed in the isomeric 5-haloresorcinols, resulting in very highly abundant [M ? Hal]⁺ ions. This behavior suggests that a ‘hidden hydrogen transfer’ accompanies the elimination of the halogen atom from the molecular ions of 4-haloresorcinols.     

Stereochemical studies 87saturated heterdcycles 82: Synthesis and steric structure of steredisomeric n-substituted tetrahydro-1,3-oxazines fused with norbornane or norbornene

$\text{diendo}$- and $\text{diexo}$-2-Methylamino and 2-benzylamino-3-hydroxymethylbicyclo [2.2.1]heptanes and the corresponding bicycio [2.2.1] heptenes ($\text{5a}$ -$\text{d}$, $\text{7a}$ -$\text{d}$) were synthesized from β-amino acid esters containing the norbornane or norbornene skeleton ($\text{3a}$-$\text{d}$). The aminoalcohols were converted to 5,8- methano -3,1-benzoxazines by reaction with formaldehyde. As established by ¹H and ¹³C NMR spectroscopy, the predominant conformation is $\text{endo - boat}$ ($\text{B}$) for the $\text{diexo}$, and $\text{exo - boat}$ ($\text{E}$) for the $\text{diendo}$ derivatives.     

Titration of fluoride with lanthanum chloride applying the biamperometric and the bipotentiometric end-point detection

Summary The possibilities of the biamperometric as well as of the bipotentiometric end-point determination in the titration of potassium fluoride with lanthanum chloride using pairs of antimony, bismuth, tin and quinhydrone electrodes (metal phase platinum, palladium and gold) were investigated. In unbuffered fluoride solutions which contained 75 % of ethanol at the titration end-point, an amount of 5.72 mg of KF was determined with an average deviation of <0.8%. The results obtained are compared with those of the potentiometric titration proving a good agreement.

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Fluoridtitration mit Lanthanchlorid unter Anwendung der biamperometrischen und bipotentiometrischen Endpunkt-bestimmung

Zusammenfassung Die Möglichkeiten der biamperometrischen und der bipotentiometrischen Endpunktbestimmung bei der Kaliumfluoridtitration mit Lanthanchlorid wurden unter Anwendung von Antimon-, Wismut-, Zinn- und Chinhydronelektrodenpaaren (Metallphase Platinum, Palladium und Gold) untersucht. In ungepufferten Fluoridlösungen mit 75 % Äthanolgehalt am Titrationsendpunkt wurden 5,72 mg Kaliumfluorid mit einer mittleren Abweichung von <0,8% bestimmt. Die erhaltenen Ergebnisse stimmten gut mit denen von potentiometrischer Titration überein.

Some of the results of this work have been reported at Euroanalysis II, Budapest, August 25–30, 1975.